Why is intermediate binding strength best for a catalyst?

If intermediates bind too weakly the surface cannot activate the reactant, but if they bind too strongly the products cannot desorb; the balance described by the Sabatier principle gives a maximum rate at intermediate binding.

Why is the oxygen reduction reaction a major challenge?

It involves transferring four electrons and protons through several intermediates whose binding energies are linked, so no single surface binds all of them optimally, leaving an intrinsic overpotential that limits fuel-cell efficiency.

Electrocatalysis

Electrocatalysis is the acceleration of electrode reactions by catalytic surfaces that lower the overpotential needed to drive them, central to the efficiency of energy-conversion devices.

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Definition

The study and practice of catalyzing electrode reactions at the electrode–electrolyte interface, reducing the overpotential required to achieve useful reaction rates.

Scope

This topic covers the principles of electrocatalysis: how an electrode material's binding of reaction intermediates governs reaction rate, the volcano relationships and Sabatier principle that identify optimal catalysts, the key reactions of energy technology such as hydrogen evolution, oxygen reduction, and oxygen evolution, and the computational descriptors used to design catalysts. It connects surface chemistry to device performance.

Core questions

How does an electrode surface lower the activation barrier of an electrode reaction?
Why does optimal catalytic activity occur at intermediate binding strength of reaction intermediates?
What makes the oxygen reduction and oxygen evolution reactions so difficult to catalyze?
How do computational descriptors guide the design of new electrocatalysts?

Key theories

Sabatier principle and volcano relationships: Catalytic activity is maximized at intermediate binding of reaction intermediates—strong enough to activate reactants but weak enough to release products—producing a volcano-shaped dependence of rate on binding energy.
Computational descriptor-based design: Density-functional calculations of intermediate adsorption energies provide descriptors that predict overpotentials, enabling rational screening and design of electrocatalysts for reactions such as oxygen reduction.

Clinical relevance

Electrocatalysts determine the efficiency and cost of fuel cells, water electrolyzers for hydrogen production, and carbon-dioxide reduction systems; reducing reliance on scarce platinum-group metals through better catalysts is a key target for clean-energy technology.

History

Empirical correlations between electrode material and activity, such as Trasatti's hydrogen-evolution volcano in the 1970s, were placed on a quantitative computational footing by Nørskov and coworkers in the 2000s, ushering in descriptor-based catalyst design now standard in the field.

Key figures

Jens K. Nørskov
Paul Sabatier
Sergio Trasatti
Thomas F. Jaramillo

Seminal works

norskov2004
seh2017
bard2001

Frequently asked questions

Why is intermediate binding strength best for a catalyst?: If intermediates bind too weakly the surface cannot activate the reactant, but if they bind too strongly the products cannot desorb; the balance described by the Sabatier principle gives a maximum rate at intermediate binding.
Why is the oxygen reduction reaction a major challenge?: It involves transferring four electrons and protons through several intermediates whose binding energies are linked, so no single surface binds all of them optimally, leaving an intrinsic overpotential that limits fuel-cell efficiency.